<template>
  <button>Hover me</button>
</template>
<style scoped>
button {
  border: 0;
  border-radius: 10px;
  background: hsl(236, 32%, 26%);
  text-transform: uppercase;
  color: white;
  font-size: 16px;
  font-weight: bold;
  padding: 0.5em 1em;
  outline: none;
  position: relative;
  transition: border-radius 3s;
  -webkit-transition: border-radius 3s;
}

button:hover {
   border-bottom-right-radius: 50px;
   border-top-left-radius: 50px;
   border-bottom-left-radius: 10px;
   border-top-right-radius: 10px;
}
</style>